NASA recently signed on to test a new
polymer-based radiation-blocking vest for astronauts, called
AstroRad, on its next mission around the moon.

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Musk, meanwhile, has said his new
Big Falcon Rocket will use water to block radiation, though
only during emergencies.

"Ambient radiation damage is not significant for our transit
times," Musk said during an Oct. 2017 chat on Reddit. "Just need a
solar storm shelter, which is a small part of the ship."

But just how bad is the problem of radiation in space?

The graphic below - created using data provided by NASA, the EPA, FDA, NRC, scientific journals, and other
sources - compares various exposure levels in scenarios both
familiar and far-flung. Hover over a category box to see how it
compares.

Musk has "aspirational" hopes to launch a round-trip mission to
the red planet with humans
in 2024, but the trip could total a year, and astronauts may
spend about 500 days on Mars' surface.

The whole journey would expose astronauts to about 1,000
millisieverts - depending on how many
solar storms belch high-energy particles toward Mars, and
whether the first entity to reach the planet actually
lands on it.

This means the first Martian explorers could get roughly eight
times the amount of radiation that a radiation worker's annual
exposure is limited to each year. The space travelers would get
about one-third of the way toward hitting a NASA astronaut's
maximum lifetime exposure limit (2,500-3,250 mSv).

Where the radiation comes from - and why cancer isn't the only
danger

Two main types of radiation in space are extremely harmful to
humans: protons spewed out by the sun and cosmic rays. These
high-energy particles and the secondary radiation they create
penetrate deep into cells, promoting chronic and sometimes deadly
diseases such as cancer.

Earth's magnetic field and atmosphere protect us by deflecting
and absorbing most of this energy.

"The background radiation rates on the ground are 100 times to
1,000 times smaller than they would be above the atmosphere in
free space," Edward Semones, a radiation health officer at NASA's
Johnson Space Center, previously told Business Insider.

Cancer is a major risk of radiation exposure, but there are more
immediate and surprising symptoms. Deep-space radiation might
promote cataracts and impair eyesight. Even high-flying
commercial-airline workers face that risk because of the
thinner atmosphere.

Animal-based experiments also suggest radiation could damage the
nervous system, including the brain, which might impair
astronauts' focus and memory.

Doing battle with deep-space radiation

Prototypes of the AstroRad radiation shield suit for deep-space travel.

source

Amir Cohen/Reuters

NASA's potential use of AstroRad vests and Musk's solar-storm
shelter would just be a starting point for Mars adventurers and
colonists.

The more thick and heavy shielding there is between a person and
the vacuum, the better. Semones said about 20 centimeters of
water can soak up most space radiation. Yet water is dense and
expensive to launch from Earth into space.

One solution is for Mars colonization missions to use
Phobos, the planet's largest moon, as a pit stop since it
likely harbors water ice just below its ruddy surface. Probes
drilled into Phobos could heat and melt the ice, pump the water
into elastic cells that surround a spacecraft, and shield a crew
from radiation.

More radical solutions for radiation have also been proposed.
Christopher Mason, a geneticist and biomedical researcher,
suggests creating transgenic humans as part of a 10-phase,
"500-year plan" to colonize space. His concept is to use a
technology like CRISPR to
edit a space flier's genome to constantly repair, as Mason
put it, "do not disturb" regions that lead to cancers and other
problems.

"You can't dismiss it as an idea, but right now but we don't know
the mechanisms," Semones said of that far-fetched plan. (About
1,000 genes are estimated to be involved in cancer alone.)

caption

A concept for an artificial magnetic shield that would prevent a terraformed Martian atmosphere from being blown into space by solar storms of high-energy particles.

Ultimately, colonists may try to
terraform Mars - a deliberate and unprecedented act of
climate change.

Frozen carbon dioxide at the Martian poles could be turned into
greenhouse gases in order to create a radiation-absorbing
atmosphere that would insulate the surface. Plants could then
convert the thin air into oxygen and, over hundreds of years,
temperatures may warm enough to melt hidden water and make it
again flow on Mars' surface. One day, that could even permit
spacesuit-free excursions.

Jim Green, the former head of NASA's planetary science division,
has proposed building an
artificial magnetic shield for Mars to protect a hypothetical
nascent atmosphere from the sun's proton radiation, which might
otherwise blow the air into space.

"This may sound 'fanciful' but new research is starting to emerge
revealing that a miniature magnetosphere can be used to protect
humans and spacecraft," Green and other researchers wrote in
a brief study of the concept
in 2017. "If this can be achieved in a lifetime, the colonization
of Mars would not be far away."